Re: [PATCH net-next v2] nfc: Allow to create multiple virtual nci devices

On Thu, 3 Nov 2022 at 17:59, Bongsu Jeon [off-list ref] wrote:

On Fri, Nov 4, 2022 at 3:19 AM Dmitry Vyukov[off-list ref] wrote:

quoted

The current virtual nci driver is great for testing and fuzzing.
But it allows to create at most one "global" device which does not allow
to run parallel tests and harms fuzzing isolation and reproducibility.
Restructure the driver to allow creation of multiple independent devices.
This should be backwards compatible for existing tests.

Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Bongsu Jeon <bongsu.jeon@samsung.com>
Cc: Krzysztof Kozlowski <redacted>
Cc: netdev@vger.kernel.org

---
Changes in v2:
- check return value of skb_clone()
- rebase onto currnet net-next
---
drivers/nfc/virtual_ncidev.c | 146 +++++++++++++++++------------------
1 file changed, 70 insertions(+), 76 deletions(-)

diff --git a/drivers/nfc/virtual_ncidev.c b/drivers/nfc/virtual_ncidev.c
index 85c06dbb2c449..48d6d09e2f6fd 100644
--- a/drivers/nfc/virtual_ncidev.c
+++ b/drivers/nfc/virtual_ncidev.c

@@ -13,12 +13,6 @@

<...>

quoted

static int virtual_ncidev_open(struct inode *inode, struct file *file)
{
      int ret = 0;
+      struct virtual_nci_dev *vdev;

-      mutex_lock(&nci_mutex);
-      if (state != virtual_ncidev_disabled) {
-              mutex_unlock(&nci_mutex);
-              return -EBUSY;
-      }
-
-      ndev = nci_allocate_device(&virtual_nci_ops, VIRTUAL_NFC_PROTOCOLS,
-                                 0, 0);
-      if (!ndev) {
-              mutex_unlock(&nci_mutex);
+      vdev = kzalloc(sizeof(*vdev), GFP_KERNEL);
+      if (!vdev)
+              return -ENOMEM;
+      vdev->ndev = nci_allocate_device(&virtual_nci_ops,
+              VIRTUAL_NFC_PROTOCOLS, 0, 0);
+      if (!vdev->ndev) {
+              kfree(vdev);
              return -ENOMEM;
      }

-      ret = nci_register_device(ndev);
+      mutex_init(&vdev->mtx);
+      init_waitqueue_head(&vdev->wq);
+      file->private_data = vdev;
+      nci_set_drvdata(vdev->ndev, vdev);
+
+      ret = nci_register_device(vdev->ndev);
      if (ret < 0) {
-              nci_free_device(ndev);
-              mutex_unlock(&nci_mutex);
+              mutex_destroy(&vdev->mtx);
+              nci_free_device(vdev->ndev);
+              kfree(vdev);
              return ret;
      }
-      state = virtual_ncidev_enabled;
-      mutex_unlock(&nci_mutex);

      return 0;
}

static int virtual_ncidev_close(struct inode *inode, struct file *file)
{
-      mutex_lock(&nci_mutex);
-
-      if (state == virtual_ncidev_enabled) {
-              state = virtual_ncidev_disabling;
-              mutex_unlock(&nci_mutex);
+      struct virtual_nci_dev *vdev = file->private_data;

-              nci_unregister_device(ndev);
-              nci_free_device(ndev);
-
-              mutex_lock(&nci_mutex);
-      }
-
-      state = virtual_ncidev_disabled;
-      mutex_unlock(&nci_mutex);
+      nci_unregister_device(vdev->ndev);
+      nci_free_device(vdev->ndev);
+      mutex_destroy(&vdev->mtx);

    Isn't kfree(vdev) necessary?

You are right. Sent v3 with the fix.